The present invention relates to the monitoring of a telecommunication network, and more particularly to a monitoring device and method for determining post dial delay actually perceived by a user.
The quality of service (QoS) provided by a telephone network depends upon a number of factors, among which major roles are played by availability, reliability and call clarity. The availability is related to the actual possibility of gaining access to a service once a request has been forwarded, and to the time it takes to complete such an operation. The reliability from a general point of view refers to the customer expectation of maintaining access to the service as long as needed without interruptions. The call clarity is mainly associated with the intelligibility of the information delivered by the network, i.e., the speech quality for telephone networks.
Assessing QoS is a fundamental task for network operators to promptly highlight malfunctions and to detect possible anomalies in order to avoid customer dissatisfaction, and to verify Service Level Agreement (SLA) conformance. In the evolving telecommunication scenario more and more often traditional local networks are remotely interconnected by means of long distance third party carriers. These carriers may offer cost effective solutions at a reasonably high QoS by exploiting emerging communication technologies. Moreover modern international networks have evolved from point-to-point networks interconnecting different countries to more complex networks with multiple routes between countries. As a consequence the choice of the best route is made on a comparative basis as a trade-off between QoS and costs.
Network operators show therefore an increasing interest in dedicated instrumentation able to appropriately monitor network performance. In-Service Nonintrusive Measurement Devices (INMDs) are suitable for assessing QoS basically by monitoring the signaling associated with calls in progress. Amongst the parameters that an INMD may evaluate by monitoring the signaling, such as the Answer Seizure Ratio (ASR), the Rejected Calls Ratio (RCR) and the Incomplete Calls Ratio (ICR), the Post Dial Delay (PDD) covers a very important role where there is need for comparing different routes to the same destination or to assess the performance of the current route being used.
PDD is defined as the time interval between the end of user or terminal equipment dialing and the reception of an appropriate network message. Such a delay, associated with connection establishment, impacts primarily on customer satisfaction since it is directly perceived by the user. Also it impacts on the costs incurred by the local operators when routing their traffic through long distance carriers since the calls are invoiced as soon as connection establishment is required.
Traditional measurement systems provide estimates of PDD by observing the signaling messages within the data channel of the network, and a typical approach is illustrated in FIG. 1. A first estimate may be easily obtained by calculating the time interval between the seizure and the first network response in the backward direction, as shown in FIG. 2. In some circumstances such an estimate may be acceptable since it fixes a lower boundary, but only partial information is gained about the actual network behavior. Another estimate of PDD may be obtained by calculating the time interval between the seizure and the receipt of answer supervision. However as seen from FIG. 2 such an interval, even if it provides an upper boundary for PDD, is strictly dependent on the customer behavior and therefore is not suitable as an absolute measure.
What is desired is a more effective measurement of PDD that is suitable as an absolute measure of telecommunication network performance.
Accordingly the present invention provides a monitor device and method for determining an absolute measure of telecommunication network performance. Signaling information on a data channel of the telecommunication network is monitored to detect the end of dialing, resetting a post dial delay (PDD) counter at that point. Then an associated voice channel of the telecommunication network is monitored until a useful signal is detected, such as a ringing tone. At that time the PDD counter is stopped and the contents reflect the absolute PDD for the call. Statistical analysis of PDD over multiple samples provides a measure of telecommunication network performance for Service Level Agreement (SLA) conformance.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.